1. Field of the Disclosure
The following is directed to a method of forming a semiconductive substrate, and particularly a substrate including a release layer for use in forming LED or LD devices.
2. Description of the Related Art
Semiconductive-based compounds, including Group III-V materials, such as gallium nitride (GaN), ternary compounds, such as, indium gallium nitride (InGaN) and gallium aluminum nitride (GaAlN), and even the quaternary compounds (AlaInN) are direct band gap semiconductors. Such materials have been recognized as having great potential for short wavelength emission, and thus suitable for use in the manufacturing of light emitting diodes (LEDs), laser diodes (LDs), UV detectors, and high-temperature electronics devices.
However, the development of such semiconductive materials has been hampered by difficulties surrounding the processing of such materials, particularly the formation of high-quality single crystalline forms of the material, which are required for manufacturing of short wavelength emission electronics. GaN is not found as a naturally occurring compound, and thus cannot be melted and pulled from a boule like silicon, gallium arsenide, or sapphire, because at usual pressures its theoretical melting temperature exceeds its dissociation temperature. As an alternative, the industry has turned to formation of bulk GaN crystals using epitaxial growth processes. However, problems still remain with the epitaxial approach, including the formation of suitable low defect density bulk GaN material.
The existence of extended defects (threading dislocations, stacking faults, and antiphase boundaries) leads to significantly deteriorated performances and results in a shortened operating lifetime of devices. More specifically, the dislocations behave as nonradiative centres, thus reducing the light-emitting efficiency of light-emitting diodes and laser diodes made from these materials. These dislocations also increase the dark current. Although threading dislocations have not prevented the development of high-brightness light-emitting diodes, the dislocations cause excessive reverse-bias leakage currents in p-n junction devices such as high-electron-mobility transistors, field-effect transistors and other electronic devices. Further, the dislocations can act as strong scattering centres for carriers, thus reducing the mobility of electrons and holes, limiting the performance of many semiconductor devices.